Both public and private organizations require accurate specification of the Earth's atmosphere at a given time or under specified input conditions. Applications include, but are not limited to: (a) planning of travel and other enterprises; (b) orbit determination and prediction of space objects in low-Earth-orbit or ballistic trajectories; (c) space object re-entry prediction (including for new commercial space tourism endeavors); and (d) radiowave absorption and propagation calculations for radars, communication, and geolocation.
Numerical Weather Prediction (NWP) systems routinely provide near-real-time specification and forecasts of the lower atmosphere (below about 50 km altitude), but no NWP system exists for the upper atmosphere (above 50 km), primarily because of the lack of regular, reliable global measurements and the immaturity of upper atmospheric models that solve the fundamental dynamical equations of physics and chemistry. Instead, empirical models are widely used for upper atmospheric specification and prediction.
Empirical atmosphere models specify key properties of the atmosphere (e.g., temperature, density) as a function of input conditions (e.g., location, day of year, etc.), consistent with available historical measurements. They are also accurately called climatological models, because they describe the average state of the atmosphere under specified conditions. In the upper atmosphere, the traditional concept of ‘climatology’ is extended to include the average response of the atmosphere to short-term variations in extreme ultra violet energy flux from the Sun, to which the upper atmosphere is very sensitive.
Although empirical models of Earth's atmosphere are most commonly used for upper atmospheric specification, they are also used in numerous lower atmospheric applications. Their compact encapsulation of measurement-based climatology provides a fast means of specifying the atmosphere when time-specific NWP is not necessary or desirable. Empirical models are used in the lower atmosphere, for example, in the estimation of exposure to harmful solar and galactic radiation during commercial aviation flights. Furthermore, NWP is not available for the atmospheres of other planets, and empirical whole-atmosphere models are therefore used in planetary exploration and scientific research.
Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.